Relative potency factors calculation

Relative potency factors (RPFs) describe the potency of substances with respect to a defined effect, relative to the potency of a chosen index substance. RPFs can be given as data or computed from hazard characterisations. The RPF for substance $i$ is defined by the ratio of hazard characterisation value for the index substance ($\mathtt{ref}$) and the hazard characterisation value for substance $i$. That is,

$${\mathtt{RPF}}_i={\mathtt{POD}}_{\mathtt{ref}}/{\mathtt{POD}}_i.$$

When the hazard characterisations are resampled in the uncertainty runs, RPFs are also recomputed based on the bootstrapped hazard characterisations. In this way, RPF uncertainty can also included in the uncertainty analysis.